CN205693959U - The constant current boost circuit of a kind of DC DC and flash lamp circuit - Google Patents

Abstract

The utility model relates to the technical field of boosting circuits, in particular to a DC-DC constant current boosting circuit and a flash lamp circuit. An energy storage capacitor, the high-voltage energy storage capacitor is connected to the flash tube in the flash lamp; the primary winding of the flyback transformer is connected with a PWM switch circuit, and the PWM switch circuit is connected with a current feedback circuit, and the flyback The secondary winding of the type transformer is connected with a comparison circuit, and the comparison circuit is used to send a corresponding waveform signal to the PWM control circuit; the PWM control circuit is connected to the PWM switch circuit for The size of the signal or the content of the waveform signal sends a PWM control signal to the PWM switch circuit; the utility model has constant boosting current, high conversion efficiency, small power loss, stable operation and high work efficiency.

Description

A DC-DC constant current boost circuit and flash lamp circuit

technical field

The utility model relates to the technical field of a flashlight booster circuit, in particular to a DC-DC constant current booster circuit and a flashlight circuit.

Background technique

With the gradual popularization of photography, as the main accessory of the camera, the flashlight is used more and more; in the flashlight, there is a boost circuit, which is used to charge the high-voltage energy storage capacitor on the flashlight. However, in the existing flash booster circuit, it has the following disadvantages: 1. The boost current is too large, which greatly affects the service life of the battery; 3. There is uncertainty in the boosting time; 4. The battery voltage fluctuates greatly during the boosting process, which easily affects the stability of the entire circuit.

Contents of the invention

In order to overcome the above defects, the purpose of this utility model is to provide a DC-DC constant current boost circuit and a flash lamp circuit.

The purpose of this utility model is achieved through the following technical solutions:

The utility model is a DC-DC constant current step-up circuit, which is arranged in a flash lamp, comprising:

A power input circuit, the power input circuit is used to connect with the power supply, and the output end of the power input circuit is connected with the primary winding of the flyback transformer;

The flyback transformer is used to step up the voltage passing through it to obtain a high voltage voltage, and the secondary winding of the flyback transformer is connected to a rectifier circuit;

The rectification circuit rectifies the high-voltage voltage output from the flyback transformer into a DC high-voltage voltage, and then inputs it into the high-voltage energy storage capacitor;

The high-voltage energy storage capacitor is connected to the flash tube in the flash lamp, and it is used to provide the working voltage for the flash tube;

The primary winding of the flyback transformer is connected with a PWM switch circuit, and the PWM switch circuit is used to adjust the working state of the flyback transformer;

The PWM switch circuit is connected with a current feedback circuit, and the current feedback circuit is used to collect the current signal passing through the PWM switch circuit to obtain a sampling current, and deliver the sampling current to the PWM control circuit;

The secondary winding of the flyback transformer is connected with a comparison circuit, which is used to obtain the voltage value on the secondary winding of the flyback transformer, and compare the voltage value on the secondary winding with the preset comparing the first voltage value, and sending a corresponding waveform signal to the PWM control circuit according to the comparison result;

The PWM control circuit is connected with the PWM switch circuit, and is used to send a PWM control signal to the PWM switch circuit according to the magnitude of the received current signal or the content of the waveform signal.

Further, the high-voltage energy storage capacitor is connected with a voltage sampling circuit, and the voltage sampling circuit collects the working voltage output by the high-voltage energy storage capacitor, and transmits the collected working voltage to the comparison circuit;

The comparison circuit compares the received working voltage with a preset second voltage value, and if the comparison result is higher than the second voltage value, drives the overvoltage protection circuit;

The overvoltage protection circuit is respectively connected with the comparison circuit and the PWM control circuit, and is used for turning off the PWM control circuit according to the drive of the comparison circuit.

Further, a buffer circuit is provided between the connection between the PWM switch circuit and the flyback transformer and the power input circuit, and the buffer circuit is used to limit the leakage inductance and reflected voltage of the flyback transformer.

Further, the PWM control circuit includes: a power control chip, 6 pins of the power control chip output a PWM control signal, and the PWM control signal is input to the input terminal of the MOS transistor in the PWM switch circuit; the The current feedback circuit is connected to the 3 pins of the power control chip, which provides sampling current for the power control chip; the external main control signal enters the 2 pin of the power control chip through the diode D2, and the external main control signal passes through the diode D2 After D2, it is connected to 8 pins of the power control chip at the same time, and the 8 pins are reference voltage output pins.

Further, the comparison circuit includes: a comparator chip, and the working voltage collected by the voltage sampling circuit is input into pin 5 of the comparator chip, and is compared with the voltage on pin 6 of the comparator chip. Compared, the voltage on the 6 pins of the comparator chip is provided by the 8th pin of the power control chip, and the voltage on the 8th pin of the power control chip is passed through the filter capacitor C12 and the parallel voltage dividing resistor R18 and resistor R16 and then input to pin 6 of the comparator chip; pin 7 of the comparator chip is connected to the overvoltage protection circuit; one end of the secondary winding of the flyback transformer is connected to the ground through resistor R22, It is also connected to pin 2 and pin 8 of the comparator chip through resistor R15 and resistor R14. After comparing the voltages on pin 2 and pin 3 of the comparator chip, pin 1 of the comparator chip outputs the corresponding The waveform signal is coupled to the base of the transistor Q3 through the capacitor C8, the E pole of the transistor Q3 is connected to the 8-pin of the power control chip, and the C pole of the transistor Q3 is connected to the base of the transistor Q2. The E pole of the transistor Q2 is grounded, and the C pole is connected to pin 3 of the power control chip.

Further, the snubber circuit includes: a diode D7, the cathode of the diode D7 is connected to the power input circuit and one end of the primary winding of the flyback transformer, the anode thereof is connected to the cathode of the diode D6 and one end of the capacitor C2, and the anode of the diode D6 is connected to the inductor One end of L1 and the other end of the inductor L1 are grounded, and the other end of the capacitor C2 is connected to the other end of the primary winding of the flyback transformer.

The utility model relates to a flashlight circuit, comprising: a battery, a flashlight tube, and the above-mentioned DC-DC constant current boost circuit, the battery and the power input circuit in the DC-DC constant current charge boost circuit The flash tube is connected to the high-voltage energy storage capacitor.

Further, the utility model also includes: a main controller, the main controller is connected with the PWM control circuit, and is used to provide a main control signal for the PWM control circuit.

The utility model has constant boosting current, high conversion efficiency, small power loss, stable work and high work efficiency.

Description of drawings

For ease of description, the utility model is described in detail by the following preferred embodiments and accompanying drawings.

Fig. 1 is the schematic diagram of the circuit principle of the constant current step-up circuit of the present utility model;

FIG. 2 is a schematic diagram of the circuit structure of the constant current boost circuit of the present invention.

detailed description

In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model, and are not intended to limit the utility model.

Please refer to Fig. 1 to Fig. 2, the utility model is a DC-DC constant current step-up circuit, comprising:

A power input circuit 1, the power input circuit 1 is used to be connected to a power supply, and the output end of the power input circuit 1 is connected to the primary winding of the flyback transformer 3;

The flyback transformer 3 is used to boost the voltage passing through it to obtain a high-voltage voltage, and the secondary winding of the flyback transformer 3 is connected to a rectifier circuit; it can convert the low-voltage DC of the power supply input circuit 1 It is a high-voltage DC voltage, which can reach the required voltage value according to the turns ratio of the transformer;

The rectifier circuit 4 rectifies the high-voltage voltage output from the flyback transformer 3 into a DC high-voltage voltage, and then inputs it into the high-voltage energy storage capacitor;

The high-voltage energy storage capacitor 5 is connected to the flash tube in the flash lamp, and is used to provide an operating voltage for the flash tube;

The primary winding of the flyback transformer 3 is connected with a PWM switch circuit 8, and the PWM switch circuit 8 is used to adjust the working state of the flyback transformer 3;

The PWM switch circuit 8 is connected with a current feedback circuit 10, and the current feedback circuit 10 is used to collect the current signal passing through the PWM switch circuit 8 to obtain a sampling current, and deliver the sampling current to the PWM control circuit 11 ;

The secondary winding of the flyback transformer 3 is connected with a comparison circuit 9, and the comparison circuit 9 is used to obtain the voltage value on the secondary winding of the flyback transformer 3, and the voltage value on the secondary winding Compared with the preset first voltage value, and according to the comparison result, a corresponding waveform signal is sent to the PWM control circuit 11; the function of the comparison circuit 9 is to compare the secondary signal of the flyback transformer 3 and output The corresponding waveform is given to the PWM control circuit 11. At the same time, the voltage sampling circuit samples the high-voltage signal of the high-voltage energy storage capacitor 5 and inputs it to the comparison circuit 9. If the voltage is higher than the highest safe voltage, the output signal of the comparator is turned off by the overvoltage protection circuit 7. Cut off the output of the PWM control circuit 11, so that the boost circuit stops working, thereby protecting the safety of the entire circuit;

The PWM control circuit 11 is connected with the PWM switch circuit 8, and is used to send a PWM control signal to the PWM switch circuit 8 according to the magnitude of the received current signal or the content of the waveform signal; its function is to output a PWM waveform To control the switching and closing functions of the PWM switch circuit 8, it can drive the PWM switch circuit 8 according to the signals input by the current feedback circuit 10, the comparison circuit 9, and the external main control circuit to output PWM waveforms with different duty ratios;

Further, the high-voltage energy storage capacitor 5 is connected with a voltage sampling circuit 6, and the voltage sampling circuit 6 collects the working voltage output by the high-voltage energy storage capacitor 5, and sends the collected working voltage to the comparison Circuit 9 carries out transmission;

The comparison circuit 9 compares the received operating voltage with a preset second voltage value, and if the comparison result is higher than the second voltage value, drives the overvoltage protection circuit 7;

The overvoltage protection circuit 7 is respectively connected with the comparison circuit 9 and the PWM control circuit 11 , and is used for turning off the PWM control circuit 11 according to the drive of the comparison circuit 9 .

Further, a snubber circuit 2 is provided between the connection between the PWM switch circuit 8 and the flyback transformer 3 and the power supply input circuit 1, and the snubber circuit 2 is used to perform the leakage inductance and reflected voltage of the flyback transformer 3 Limitation; mainly used to limit the superposition of peak voltage and secondary coil reflected voltage caused by the energy of the flyback transformer leakage inductance when the MOS tube in the PWM switching circuit 8 is turned off, reducing circuit loss and improving stability.

Further, the PWM control circuit 11 includes: a power control chip U1, the 6 pins of the power control chip U1 output a PWM control signal, and the PWM control signal is input to the input of the MOS transistor in the PWM switch circuit 8 terminal; the current feedback circuit 10 is connected to the 3 pins of the power control chip U1, which provides sampling current for the power control chip U1; the external main control signal enters the 2 pins of the power control chip U1 through the diode D2, And the external main control signal is connected to the 8 pin of the power control chip U1 after passing through the diode D2, and the 8 pin is the reference voltage output pin.

Further, the comparison circuit 9 includes: a comparator chip U2, the working voltage collected by the voltage sampling circuit 6 is input to the 5 pins of the comparator chip U2, and is connected to the 6 pins of the comparator chip U2. The voltage on the pin is compared, the voltage on the 6th pin of the comparator chip U2 is provided by the 8th pin of the power control chip U1, and the voltage on the 8th pin of the power control chip U1 is filtered by the capacitor C12 After the voltage dividing resistor R18 and the resistor R16 connected in parallel are input to the 6-pin of the comparator chip U2; the 7-pin of the comparator chip U2 is connected to the overvoltage protection circuit 7; the flyback transformer 3 One end of the secondary winding is connected to the ground through the resistor R22, and also connected to the 2-pin and 8-pin of the comparator chip U2 through the resistor R15 and the resistor R14, and connected to the 2-pin and 3-pin of the comparator chip U2 After the voltage comparison, the 1 pin of the comparator chip U2 outputs the corresponding waveform signal, which is coupled to the base of the transistor Q3 through the capacitor C8, and the E pole of the transistor Q3 is connected to the 8 pin of the power control chip U1 , the C pole of the transistor Q3 is connected to the base of the transistor Q2, the E pole of the transistor Q2 is grounded, and the C pole is connected to the pin 3 of the power control chip U1.

Further, the buffer circuit 2 includes: a diode D7, the cathode of the diode D7 is connected to the power input circuit 1 and one end of the primary winding of the flyback transformer 3, the anode thereof is connected to the cathode of the diode D6 and one end of the capacitor C2, the diode D6 The positive pole is connected to one end of the inductor L1 , the other end of the inductor L1 is grounded, and the other end of the capacitor C2 is connected to the other end of the primary winding of the flyback transformer 3 .

The utility model is a flashlight circuit, comprising: a battery, a flashlight tube, and the above-mentioned DC-DC constant current boost circuit, the battery and the power input circuit 1 in the DC-DC constant current boost circuit connected, the flash tube is connected to the high voltage energy storage capacitor 5 .

Further, the utility model also includes: a main controller, which is connected to the PWM control circuit 11 and used to provide the PWM control circuit 11 with a main control signal.

The concrete circuit connection relation of the present utility model is:

The power supply BAT is connected to C1 as the filter capacitor of the power supply circuit, connected to one end of the primary winding of the transformer TB1 in the flyback transformer 3, the negative pole of the diode D7 is connected to the power supply and one end of the primary winding of the transformer TB1, and the positive pole is connected to the negative pole of D6 and the C2 capacitor One end of D6, the positive pole of D6 is connected to one end of inductor L1, the other end of L1 is connected to ground, and the other end of C2 is connected to the other end of the primary winding of the transformer to form a snubber circuit 2, and the other end of the transformer winding is connected to the D pole of MOS tube T1 , the PWM control signal is output from pin 6 of the power control chip U1, connected to the G pin of the MOS tube T1 through the resistor R4, R5 is a pull-down resistor, R19 is a current detection resistor, and the current flows through R19 to the ground when the MOS tube is turned on. The voltage signal generated in R19 is connected to the 3-pin (current detection port) of U1 through the resistor R6 to adjust the PWM output waveform through the internal comparator so as to achieve the effect of constant current. U1 does not work when pin 2 of U1 is high level, and works when it is low level. When the external circuit needs to obtain high voltage, the external control signal can be connected to the negative pole of D2 to output low level, so that U1 works and outputs PWM control signal. Drive the MOS tube and then drive the transformer to obtain the required high-voltage voltage. When the high-voltage voltage has reached the required voltage, the external control circuit can output a high level by connecting the negative pole of D2 to stop U1 from working, and the circuit will no longer boost the voltage. . The anode of D2 is connected to pin 2 of U1 and R3 at the same time, the other end of R3 is connected to the reference voltage output pin 8 of U1, the voltage is a standard fixed voltage of 4V, thereby controlling the working state of the entire boost circuit. D4 and D5 are high-voltage fast recovery diodes connected to one end of the secondary winding of the transformer to form a rectifier circuit 4, so that the capacitor C3 can obtain a DC high voltage voltage. R12, R20, R21, and C3 high-voltage positive capacitors are connected in series to the ground to form a voltage-dividing sampling circuit. The sampling voltage obtained between R20 and R21 is connected to the fifth pin of U2, and compared with the voltage of the sixth pin. The voltage of pin 6 is provided by the reference voltage output pin of pin 8 of U1, and the voltage is filtered by C12 and divided by R18 and R16. C13 is the filter capacitor of pin 6 of U2. When the voltage on capacitor C3 is higher than the overcharge When the protection voltage (this voltage can be adjusted according to the setting of the resistance value of R12, R20, R21) is higher than the voltage on the 5 pin of U2 will be higher than the voltage on the 6 pin of U2. The output level of pin 7 of comparator chip U2 is converted from the original low level to high level, and the base of Q1 transistor transistor is connected through R17, so that Q1 is turned on, and the collector voltage is pulled down to GND. C14 is a filter capacitor. Through the D1 diode and the Q4 transistor R2 bias resistor, the reference voltage 4V on the 8th pin of U1 is conducted through the E pole of the Q4 transistor transistor to the C pole to the 3 pin of U1 (current detection input pin ), since the voltage will be higher than the over-current threshold voltage of this pin, U1 will start the protection function and stop working to achieve the over-voltage protection function. One end of R1 is connected to pin 8 of U1, the other end is connected to R7, and R7 is connected to pin 3 of U1. C4 is a filter capacitor. Properly adjusting the resistance of R1 and R7 can adjust the size of the constant current in a small range. One end of the TB1 secondary winding is connected to the ground by R22, R15 and C10 are connected in parallel, one end is connected to the 2-pin input terminal of the comparator chip U2, one end of the resistor R14 is connected to the 8-pin (power supply pin) of U2, and one end is connected to the 2-pin of U2 One end of C11 is connected to pin 2 of U2 and the other end is grounded. Through the voltage comparison between pin 2 and pin 3 of U2, pin 1 of U2 outputs the corresponding voltage waveform, which is coupled to the base of Q3 transistor through C8, and Q3 The E pole of Q3 is connected to the 8 pin of U1, the C pole of Q3 is connected to R11, C5, C6, the other end of C6 is connected to the base of Q2 transistor, the E pole of Q2 is grounded, the C pole is connected to the 3 pin of U1, C5 The other end of the circuit is connected to R8 C7 to adjust the frequency and duty cycle of the output drive waveform to achieve the constant current boost effect of the entire circuit.

The above descriptions are only preferred embodiments of the present utility model, and are not intended to limit the present utility model. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present utility model shall be included in this utility model. within the scope of protection of utility models.

Claims (8)

1. A constant current step-up circuit of DC-DC, which is arranged in a flashlight, is characterized in that, comprising: A power input circuit, the power input circuit is used to connect with the power supply, and the output end of the power input circuit is connected with the primary winding of the flyback transformer; The flyback transformer is used to step up the voltage passing through it to obtain a high voltage voltage, and the secondary winding of the flyback transformer is connected to a rectifier circuit; The rectification circuit rectifies the high-voltage voltage output from the flyback transformer into a DC high-voltage voltage, and then inputs it into the high-voltage energy storage capacitor; The high-voltage energy storage capacitor is connected to the flash tube in the flash lamp, and it is used to provide the working voltage for the flash tube; The primary winding of the flyback transformer is connected with a PWM switch circuit, and the PWM switch circuit is used to adjust the working state of the flyback transformer; The PWM switch circuit is connected with a current feedback circuit, and the current feedback circuit is used to collect the current signal passing through the PWM switch circuit to obtain a sampling current, and deliver the sampling current to the PWM control circuit; The secondary winding of the flyback transformer is connected with a comparison circuit, which is used to obtain the voltage value on the secondary winding of the flyback transformer, and compare the voltage value on the secondary winding with the preset comparing the first voltage value, and sending a corresponding waveform signal to the PWM control circuit according to the comparison result; The PWM control circuit is connected with the PWM switch circuit, and is used to send a PWM control signal to the PWM switch circuit according to the magnitude of the received current signal or the content of the waveform signal. 2. The constant current step-up circuit of DC-DC according to claim 1, characterized in that, the high voltage energy storage capacitor is connected with a voltage sampling circuit, and the output voltage of the high voltage energy storage capacitor by the voltage sampling circuit is collecting the working voltage, and sending the collected working voltage to the comparison circuit; The comparison circuit compares the received working voltage with a preset second voltage value, and if the comparison result is higher than the second voltage value, drives the overvoltage protection circuit; The overvoltage protection circuit is respectively connected with the comparison circuit and the PWM control circuit, and is used for turning off the PWM control circuit according to the drive of the comparison circuit. 3. The constant current step-up circuit of DC-DC according to claim 2, characterized in that, a buffer circuit is provided between the connection between the PWM switch circuit and the flyback transformer and the power input circuit, and the buffer circuit The circuit is used to limit the leakage inductance and reflected voltage of the flyback transformer. 4. The DC-DC constant current step-up circuit according to claim 3, wherein the PWM control circuit comprises: a power control chip, and 6 pins of the power control chip output a PWM control signal, so The PWM control signal is input to the input terminal of the MOS tube in the PWM switch circuit; the current feedback circuit is connected to the 3 pins of the power control chip, which provides sampling current for the power control chip; the external main control The signal enters the pin 2 of the power control chip through the diode D2, and the external main control signal passes through the diode D2, and is connected to the pin 8 of the power control chip at the same time, and the pin 8 is the reference voltage output pin. 5. The DC-DC constant current boost circuit according to claim 4, wherein the comparison circuit comprises: a comparator chip, and the operating voltage collected by the voltage sampling circuit is input to the comparator 5 pins in the chip, and compare with the voltage on the 6 pins of the comparator chip, the voltage on the 6 pins of the comparator chip is provided by the 8th pin of the power control chip, the power control The voltage on the 8th pin of the chip is input to the 6th pin of the comparator chip after passing through the filter capacitor C12 and the parallel voltage dividing resistor R18 and resistor R16; the 7th pin of the comparator chip is connected with the overvoltage protection circuit One end of the secondary winding of the flyback transformer is connected to the ground through the resistor R22 and also connected to the 2-pin and 8-pin of the comparator chip through the resistor R15 and the resistor R14, and through the 2-pin of the comparator chip After comparing the voltages on pin 3 with pin 3, pin 1 of the comparator chip outputs a corresponding waveform signal, which is coupled to the base of transistor Q3 through capacitor C8, and the pole E of transistor Q3 is connected to the power control chip. 8-pin connection, the C pole of the transistor Q3 is connected to the base of the transistor Q2, the E pole of the transistor Q2 is grounded, and the C pole is connected to the 3 pin of the power control chip. 6. The DC-DC constant current step-up circuit according to claim 5, wherein the snubber circuit comprises: a diode D7, the cathode of which is connected to the power supply input circuit and the primary winding of the flyback transformer One end, the anode of which is connected to the cathode of diode D6 and one end of capacitor C2, the anode of diode D6 is connected to one end of inductor L1, the other end of inductor L1 is grounded, and the other end of capacitor C2 is connected to the other end of the primary winding of the flyback transformer . 7. A flash circuit, characterized in that it comprises: a battery, a flash tube and the DC-DC constant current boost circuit according to any one of claims 1 to 6, the battery and the DC-DC The power input circuit in the constant current boost circuit is connected, and the flash tube is connected with the high voltage energy storage capacitor. 8. The flash light circuit according to claim 7, further comprising: a main controller connected to the PWM control circuit for providing a main control signal to the PWM control circuit.